Thermal Spray For Solar Concentrator Fabrication

ABSTRACT

A solar concentrator including a substantially-transparent optical element, a reflective material disposed on a convex surface of the optical element, an insulator layer on the reflective material, a conductive material that is thermal sprayed onto the insulator layer, and a solar cell mounted in a central region of the convex surface and electrically coupled to the conductive material. The optical element includes a flat surface disposed opposite to the convex surface and a concave surface defined in the flat surface. The convex surface and concave surface are arranged and the reflective material is deposited such that light passing through the flat surface is reflected by the reflective material toward the concave surface, and is re-reflected by the reflective material disposed on the concave surface onto an active surface of the solar cell. Thermal spraying the conductive material may include spraying a molten metal powder onto the insulator layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser. No. 11/782,605, filed on Jul. 24, 2007 and entitled “Thermal Spray For Solar Concentrator Fabrication” and claims priority to U.S. Provisional Patent Application Ser. No. 60/899,150, filed on Feb. 2, 2007 and entitled “Concentrated Photovoltaic Energy Designs”, the contents of which are incorporated herein by reference for all purposes.

BACKGROUND

1. Field

Some embodiments generally relate to the collection and concentration of solar radiation. More specifically, embodiments may relate to systems to efficiently fabricate solar radiation collectors.

2. Brief Description

A concentrating solar radiation collector may convert received solar radiation (i.e., sunlight) into a concentrated beam and direct the concentrated beam onto a small photovoltaic cell. The cell, in turn, converts the photons of the received beam into electrical current.

U.S. Patent Application Publication No. 2006/0231133 describes several types of concentrating solar collectors. As described therein, a concentrating solar collector may include reflective material for directing received solar radiation, conductive material to carry electrical current generated from the solar radiation, and/or insulative material to isolate various conductors from one another. Fabrication of a solar radiation collector using one or more of these materials may be unsuitably complex and costly.

For example, conventional techniques for depositing these materials may include evaporating or sputtering within an established vacuum. Thin film lithographic techniques are employed to create desired patterns and features in the deposited materials. Such techniques require photoresist deposition, masking, UV exposure, and subsequent etching for each layer of material. Thin film lithography may provide geometrically accuracy but entails significant expense.

SUMMARY

To address at least the foregoing, some aspects provide a method, means and/or process steps for providing a solar concentrator including a reflective material deposited over a convex surface of a substantially-transparent optical element (core), an insulator layer deposited over the reflective material, a conductive (first) material that is thermal-sprayed onto the insulator, and a solar cell mounted on the optical element and electrically coupled to the conductive material. The optical element includes a flat surface disposed opposite to the convex surface, and a concave surface formed in the flat surface, wherein the convex surface and concave surface are arranged and the reflective material is deposited such that light passing through the flat surface is reflected by the reflective material toward the concave surface.

In some aspects, thermal spraying the conductive material may include spraying a molten metal powder onto the insulator layer. Moreover, spraying the molten metal powder may include placing a stencil over the optical element and spraying a molten metal powder onto the stencil and the insulator layer.

In other aspects, the optical element also includes an aperture defined in a central region of the convex surface from which light reflected from reflective material disposed on the concave surface may pass out of the optical element to the solar cell. An electrical contact of the solar cell is coupled to the hardened metal powder, and an optically-active area of the solar cell is aligned with the aperture.

In yet other aspects, the insulator may include a powder-coated polymer.

The claims are not limited to the disclosed embodiments, however, as those in the art can readily adapt the description herein to create other embodiments and applications.

BRIEF DESCRIPTION OF THE DRAWINGS

The construction and usage of embodiments will become readily apparent from consideration of the following specification as illustrated in the accompanying drawings, in which like reference numerals designate like parts

FIG. 1 is a flow diagram of a method according to some embodiments.

FIG. 2A is a perspective view of a portion of an optical element and conductive material according to some embodiments.

FIG. 2B is a cross-sectional view of a portion of an optical element and conductive material according to some embodiments.

FIG. 3A is a perspective view of a portion of an optical element and a solar cell coupled thereto according to some embodiments.

FIG. 3B is a perspective view of a portion of an optical element and a solar cell coupled thereto according to some embodiments.

FIG. 4 is a flow diagram of a method according to some embodiments.

FIG. 5A is a perspective view of a transparent optical element according to some embodiments.

FIG. 5B is a cross-sectional view of a transparent optical element according to some embodiments.

FIG. 6A is a perspective view of a transparent optical element with reflective material disposed thereon according to some embodiments.

FIG. 6B is a cross-sectional view of a transparent optical element with reflective material disposed thereon according to some embodiments.

FIG. 7A is a perspective view of an optical element with an electrical isolator disposed thereon according to some embodiments.

FIG. 7B is a cross-sectional view of an optical element with an electrical isolator disposed thereon according to some embodiments.

FIG. 8A is a perspective view of an optical element with conductive material disposed thereon according to some embodiments.

FIG. 8B is a cross-sectional view of an optical element with conductive material disposed thereon according to some embodiments.

FIG. 9 is a cross-sectional view of an optical element and a solar cell according to some embodiments.

DETAILED DESCRIPTION

The following description is provided to enable any person in the art to make and use the described embodiments and sets forth the best mode contemplated for carrying out some embodiments. Various modifications, however, will remain readily apparent to those in the art.

FIG. 1 is a flow diagram of process 100 according to some embodiments. Process 100 may be performed by any combination of machine, hardware, software and manual means.

Initially, at S110, a first material is thermal sprayed onto an optical element. The first material may comprise any material that is capable of being thermally-sprayed. Thermal spraying the first material may include heating a powder to a molten state and spraying the molten powder onto the optical element. The molten powder then cools on the optical element to produce a solid layer of material. In some embodiments, a stencil may be applied to the optical element before spraying the molten powder onto the optical element. The first material is therefore deposited in a pattern defined by the stencil.

The thermal spraying may be performed using a known twin wire arc process in a case that the first material is a metal. Plasma spray techniques may be employed at S110 if the first material is a metal or a ceramic. Moreover, if the first material is a polymer (e.g., polyester, epoxy, polyurethane, etc.), the first material may be powder coated onto the optical element at S110. Accordingly, the term thermal spraying encompasses at least twin wire arcing, plasma spraying (e.g., hot, cold, assisted), and powder coating.

Thermal spraying the first material onto the optical element may comprise spraying the first material onto other material(s) already deposited on the optical element. According to some embodiments, the optical element may be configured to manipulate and/or pass desired wavelengths of light. The optical element may comprise any number of disparate materials and/or elements (e.g., lenses, reflective surfaces and optically-transparent portions).

FIG. 2A is a perspective view of apparatus 200 according to some embodiments, and FIG. 2B is a cross-sectional view of apparatus 200 as shown in FIG. 2A. Apparatus 200 includes optical element 220 and conductive material 210 sprayed thereon according to some embodiments of S110. FIGS. 2A and 2B show only a portion of apparatus 200 in order to illustrate that apparatus 200 may exhibit any suitable shape or size.

Conductive material 210 may comprise any combination of one or more currently- or hereafter-known conductors, including but not limited to copper, gold and nickel. A thickness of material 210 on optical element 220 might not be as uniform as shown in FIG. 2B.

A solar cell is coupled to the optical element at S120. The coupling at S120 may comprise coupling the solar cell to other material(s) already deposited on the optical element. For example, an electrical contact of the solar cell may be coupled to conductive material deposited on the optical element. Such a coupling may form an electrical and a mechanical interconnection between the conductive material and the solar cell. Various flip-chip bonding techniques may be employed in some embodiments to couple an electrical contact of the solar cell to conductive material deposited on the optical element.

FIG. 3A is a perspective view of apparatus 200 after S120 according to some embodiments. FIG. 3B is a cross-sectional view corresponding to FIG. 3A. Solder bumps 305 of solar cell 300 are coupled to conductive material 210. Solder bumps 305 may also be respectively coupled to unshown terminals of solar cell 300.

Solar cell 300 may comprise a solar cell (e.g., a III-V cell, II-VI cell, etc.) for receiving photons from optical element 220 and generating electrical charge carriers in response thereto. In this regard, some embodiments include an opening through dielectric conductive material 210 through which solar cell 300 may receive light from optical element 220.

FIG. 4 is a flow diagram of process 400 according to some embodiments. Process 400 may be performed by any combination of machine, hardware, software and manual means.

Process 400 begins at S410, at which an optical element is obtained. The optical element may be composed of any suitable material or combination of materials. The optical element may be created using any combination of devices and systems that is or becomes known.

FIG. 5A is a perspective view of optical element 500 created at S410 according to some embodiments, and FIG. 5B is a cross-sectional view of element 500. Optical element 500 may be molded from low-iron glass at S410 using known methods. Alternatively, separate pieces may be glued or otherwise coupled together to form element 500. Optical element 500 may comprise an element of a solar concentrator according to some embodiments.

Element 500 includes convex surface 510, pedestal 520, and concave surface 530. The purposes of each portion of element 500 during operation according to some embodiments will become evident from the description below.

A reflective material is deposited on the optical element at S420. The reflective material may be intended to create one or more mirrored surfaces. Any suitable reflective material may be used, taking into account factors such as but not limited to the wavelengths of light to be reflected, bonding of the reflective material to the optical element, and cost. In some embodiments, the reflective material may include a mirror coating, a dielectric enhancement coating, and/or a protective dielectric or polymer paint coating. The reflective material may be deposited by sputtering or other physical vapor deposition, liquid deposition, etc.

FIGS. 6A and 6B show perspective and cross-sectional views, respectively, of optical element 500 after some embodiments of S420. Reflective material 540 is deposited on convex surface 510 and concave surface 530. Reflective material 540 may comprise sputtered silver or aluminum. The vertical and horizontal surfaces of pedestal 520 may be masked at S420 such that reflective material 540 is not deposited thereon, or otherwise treated to remove any reflective material 540 that is deposited thereon.

Next, at S430, a polymer is powder-coated onto the optical element. The polymer may comprise an electrical insulator, and the powder-coating may proceed according to any method that is or becomes known. The polymer may act as a mechanical buffer layer between the reflective material and conductive material. This buffer layer can also be deposited by other means such as spraying, dipping or lamination. According to some embodiments, other suitable insulators such as any dielectrics, polyester, epoxy and polyurethane are powder-coated onto the optical element at S430.

Some embodiments of S430 are depicted in FIGS. 7A and 7B. Polymer 550 is deposited on convex surface 510 or, more particularly, on reflective material 540. S615 may be executed such that polymer 550 is not deposited on the vertical and horizontal surfaces of pedestal 520. According to the illustrated embodiment, polymer 550 is not deposited on concave surface 530 (i.e., on reflective material 540 deposited on concave surface 530).

Returning to process 400, a stencil is placed on the optical element at S440 and a molten metal powder is sprayed on the stencil and the optical element at S450. The stencil may comprise a mechanical, hard or soft tooling. The stencil may cover portions of the previously-deposited polymer that are not to receive the molten metal powder. The molten metal powder may be composed of any combination of one or more metals (e.g., nickel, copper).

FIG. 8A is a perspective view and FIG. 8B is a cross-sectional view of optical element 500 after S450 according to some embodiments. Conductive material 560 covers pedestal 520 and portions of insulator 550. Conductive material 570 is also sprayed at S450 and also covers portions of insulator 550. A stencil in the shape of the illustrated gap between conductive material 560 and conductive material 570 was placed at S440. The gap may facilitate electrical isolation between conductive material 560 and conductive material 570.

Aperture 565 may comprise an exit window for light entering element 500. The stencil placed at S440 may also define aperture 565. Such a stencil may comprise a mechanical, a liquid or a solid mask which is removed (i.e., peeled or dissolved) after S450.

Although conductive materials 560 and 570 appear to extend to a uniform height above element 500, this height need not be uniform. Conductive materials 560 and 570 may create a conductive path for electrical current generated by a photovoltaic (solar) cell coupled to element 500. Conductive material 560 and conductive material 570 may also, as described in U.S. Patent Application Publication No. 2006/0231133, electrically link solar cells of adjacent solar concentrators in a solar concentrator array.

An electrical contact of a solar cell is coupled to the metal sprayed onto the optical element at S460. The electrical contact may comprise a solder bump, and any number of intermediate conductive elements such as various layers of bonding pads may be used to couple the electrical contact to the exposed portion. Coupling the electrical contact to the metal may comprise any flip-chip bonding techniques that are or become known. For example, the electrical contact may be placed on the metal using a pick-and-place machine, and the optical element and solar cell may be placed in a reflow oven to melt and subsequently cool the electrical contact.

FIG. 9 shows solder bumps 910 of solar cell 900 coupled to conductive material 560. Window 920 of solar cell 900 covers an optically-active area of solar cell 900. Accordingly, solder bumps 910 are coupled to conductive material 560 in some embodiments such that the optically-active area is aligned with aperture 565.

Apparatus 500 of FIG. 9 may generally operate in accordance with the description of aforementioned U.S. Patent Application Publication No. 2006/0231133. With reference to FIG. 9, solar rays enter surface 598 and are reflected by reflective material 540 disposed on convex surface 510. The rays are reflected toward reflective material 540 on concave surface 530, and are thereafter reflected toward aperture 565. The reflected rays pass through aperture 565 and are received by window 920 of solar cell 900. Those skilled in the art of optics will recognize that combinations of one or more other surface shapes may be utilized to concentrate solar rays onto a solar cell.

Solar cell 900 receives a substantial portion of the photon energy received at surface 598 and generates electrical current in response to the received photon energy. The electrical current may be passed to external circuitry (and/or to similar serially-connected apparatuses) through conductive material 560 and conductive material 570. In this regard, solar cell 900 may also comprise an electrical contact electrically coupled to conductive material 570. Such a contact would exhibit a polarity opposite to the polarity of the contacts to which solder bumps 910 are coupled.

The several embodiments described herein are solely for the purpose of illustration. Embodiments may include any currently or hereafter-known versions of the elements described herein. Therefore, persons in the art will recognize from this description that other embodiments may be practiced with various modifications and alterations. 

1. A method for producing a solar concentrator, the method comprising: depositing a reflective material on a convex surface substantially-transparent optical element, the optical element including a flat surface disposed opposite to the convex surface, wherein the reflective material is deposited such that light passing through the flat surface is reflected by the reflective material disposed on the convex surface; depositing an insulative material on the reflective material; and thermal spraying a conductive material onto the insulative material.
 2. The method of claim 1, wherein the optical element further includes a concave surface defined in the flat surface, the convex surface and concave surface being arranged such that said light reflected by the reflective material disposed on the convex surface is directed toward the concave surface, and wherein the method further comprises: depositing said reflective material on the concave surface of the optical element; and mounting a solar cell onto a central region of the convex surface of the optical element such that the solar cell is electrically coupled to the conductive material, wherein the reflective material is deposited on the concave surface such that said light reflected from the reflective material disposed on the convex surface is re-reflected by the reflective material disposed on the concave surface toward the solar cell.
 3. The method according to claim 2, wherein thermal spraying the conductive material comprises thermal spraying a molten metal powder onto the insulative material.
 4. The method according to claim 3, wherein thermal spraying the conductive material comprises thermal spraying one or more of gold, nickel and copper.
 5. The method according to claim 3, wherein spraying the molten metal powder onto the optical element comprises: placing a stencil on the optical element; and spraying a molten metal powder onto the stencil and the insulative material layer.
 6. The method according to claim 5, further comprising removing the stencil to expose an aperture from which light may pass out of the optical element, wherein mounting the solar cell comprises positioning the solar cell in the central region of the convex surface such that an optically-active area of the solar cell is aligned with the aperture.
 7. The method according to claim 5, wherein the stencil comprises a mechanical, hard or soft tooling.
 8. The method according to claim 1, wherein depositing the reflective material comprises depositing a mirror coating using one of sputtering, physical vapor deposition and liquid deposition.
 9. The method according to claim 1, wherein depositing the insulative material comprises depositing a powder-coated polymer.
 10. The method according to claim 1, wherein depositing the insulative material comprises a polymer using one of spraying, dipping and lamination.
 11. A solar concentrator comprising: a substantially-transparent optical element including a flat surface and a convex surface disposed opposite to the flat surface; a first reflective material layer disposed on the convex surface of the optical element, wherein the first reflective material layer is deposited such that light passing through the flat surface is reflected by the first reflective material layer into the optical element; an insulative material layer disposed on the first reflective material layer; and a thermal-sprayed conductive material layer disposed on the insulative material layer.
 12. The solar concentrator of claim 11, wherein the optical element further includes a concave surface defined in the flat surface, the convex surface and concave surface being arranged such that said light reflected by the first reflective material layer is directed toward the concave surface, wherein the solar concentrator further comprises: a second reflective material layer disposed on the concave surface of the optical element; and a solar cell mounted onto the optical element and disposed a central region of the convex surface of the optical element such that the solar cell is electrically coupled to the conductive material layer, wherein the reflective material is deposited on the concave surface such that said light reflected from the reflective material disposed on the convex surface is re-reflected by the reflective material disposed on the concave surface toward the solar cell.
 13. The solar concentrator of claim 12, wherein the conductive material layer comprises a molten metal powder.
 14. The solar concentrator according to claim 13, wherein the molten metal powder comprises one or more of gold, nickel and copper.
 15. The solar concentrator according to claim 14, wherein the optical element includes an aperture disposed in a central region of the convex surface from which light may pass out of the optical element, wherein the solar cell is positioned in the central region of the convex surface such that an optically-active area of the solar cell is aligned with the aperture.
 16. The solar concentrator according to claim 11, wherein the reflective material layer comprises a mirror coating.
 17. The solar concentrator according to claim 11, wherein the insulative material layer comprises a powder-coated polymer.
 18. The solar concentrator according to claim 11, wherein the insulative material layer comprises a polymer.
 19. A solar concentrator comprising: a substantially-transparent optical element including a flat surface, a convex surface disposed opposite to the flat surface, and a concave surface defined in the flat surface; a first reflective material layer disposed on the convex surface of the optical element; a second reflective material layer disposed on the cave surface of the optical element; an insulative material layer disposed on the first reflective material layer; a thermal-sprayed conductive material layer disposed on the insulative material layer; and a solar cell mounted onto the optical element and disposed a central region of the convex surface of the optical element such that the solar cell is electrically coupled to the conductive material layer, wherein the first and second reflective material layers are deposited and arranged by the convex and concave surfaces such that light passing through the flat surface is reflected by the first reflective material layer toward the second reflective material layer, and is re-reflected by the second reflective material layer onto the solar cell.
 20. The solar concentrator according to claim 11, wherein the first and second reflective material layers comprises a mirror coating, wherein the insulative material layer comprises a polymer, wherein thermal-sprayed conductive material layer comprises a molten metal powder including one or more of gold, nickel and copper. 